Sheet feeding apparatus with buffer function and method thereof

ABSTRACT

Disclosed is a sheet feeding apparatus having a sheet buffer function (temporal storage function), which has a simple structure without a buffer drum and feeds a present sheet and a subsequent sheet by stacking the present sheet and the subsequent sheet. The sheet feeding apparatus includes a pair of discharge rollers including a driving roller and an idle roller, a first feeding path connected to the discharge rollers, a second feeding path located at a rear of the first feeding path, branch flaps installed at a branch part of the first and second feeding paths, a sheet detecting sensor installed on the first feeding path, a cam holder for rotatably supporting both ends of a rotating shaft of the driving roller, and a cam for moving the cam holder up and down to allow the driving roller to selectively engage with the idle roller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet feeding apparatus for feeding sheets discharged from an image forming device, such as a printer or a copy machine, to a reprocessing device, such as a stapler, or a tray.

More particularly, the present invention relates to a sheet feeding apparatus having a sheet buffer function (temporal storage function), which has a simple structure without a buffer drum and can feed a present sheet and a subsequent sheet by stacking the present sheet and the subsequent sheet. 2. Description of the Related Art

In general, as shown in FIG. 1, an image processing system includes a sheet feeding apparatus 2 for feeding sheets discharged from an image forming device 1, and a sheet processing apparatus 3 for reprocessing (finishing) the sheets fed from the sheet feeding apparatus 2 or stacking the sheets onto a tray.

The sheet processing apparatus 3 can be configured to perform various reprocessing works, such as punching, bookbinding, or stapling. The sheet processing apparatus 3 including a tray 4 and a stapler 5 is illustrated in FIG. 1.

The sheet feeding apparatus 2 is disposed between the image forming device 1 and the sheet processing apparatus 3. Such a sheet feeding apparatus is disclosed in Korean Patent Registration No. 514,285, and U.S. Pat. No. 6,283,470.

The sheet feeding apparatus 2 according to the related art has the drum structure, so the structure of the sheet feeding apparatus 2 is complicated and the size of the sheet feeding apparatus 2 is enlarged.

In addition, since the sheet feeding apparatus 2 has the drum structure, it is difficult to arrange the sheets when the sheets are fed and the jam of the sheets may frequently occur.

SUMMARY

The present invention has been made to solve the problems occurring in the prior art, and the present invention provides a sheet feeding apparatus having a buffer function, in which a cam is installed in a pair of discharge rollers without a drum-type buffer and a second feeding path and a branch flap are branched from a first feeding path connected to the discharge rollers to temporally buffer previous sheets.

An object of the present invention is to provide the sheet feeding apparatus having a buffer function, which is installed on a sheet feeding path with a simple structure.

Another object of the present invention is to provide a sheet feeding apparatus having a buffer function, which may not cause the jam of the sheets and can improve the reliability.

In order to accomplish the above objects, the present invention provides a sheet feeding apparatus having a buffer function. The sheet feeding apparatus includes a pair of discharge rollers including a driving roller and an idle roller, a first feeding path connected to the discharge rollers, a second feeding path located at a rear of the first feeding path while being branched from the first feeding path, a branch flap installed at a branch part of the first and second feeding paths, a sheet detecting sensor installed on the first feeding path between the branch flap and the discharge rollers, a cam holder for rotatably supporting both ends of a rotating shaft of the driving roller, and a cam for moving the cam holder up and down to allow the driving roller to selectively engage with the idle roller.

The rotating shaft of the driving roller is connected to a reversible motor.

The cam holder has a substantially rectangular ring shape having a stepped top surface, the cam is installed in an internal cavity of the cam holder, and the cam selectively makes contact with a stepped inner surface of the cam holder.

In addition, the present invention provides a method for feeding sheets. The method includes the steps of discharging a first sheet outward through the pair of discharge rollers until a rear end of the first sheet is detected by the sheet detecting sensor as the first sheet is fed along the first feeding path, reversely driving the pair of discharge rollers as the sheet detecting sensor detects the rear end of the first sheet and moving back the first sheet by guiding the rear end of the first sheet to the second feeding path using the branch flap, driving the cam such that the driving roller and the idle roller of the discharge rollers are spaced part from each other, and returning the branch flap to an initial position thereof to allow a second sheet to be fed along the first feeding path, and allowing the driving roller and the idle roller of the discharge rollers to make contact with each other when a predetermined time has elapsed after a front end of the second sheet has passed through the sheet detecting sensor and rotating the driving roller and the idle roller of the discharge rollers in a forward direction such that the first and second sheets are simultaneously discharged out of the pair of the discharge rollers.

According to the present invention, the sheets can be discharged at the high speed without remarkably changing the structure of the sheet feeding apparatus by discharging the sheets through the steps of discharging a first sheet outward through the pair of discharge rollers until a rear end of the first sheet is detected by the sheet detecting sensor as the first sheet is fed along the first feeding path, reversely driving the pair of discharge rollers as the sheet detecting sensor detects the rear end of the first sheet and moving back the first sheet by guiding the rear end of the first sheet to the second feeding path using the branch flap, driving the cam such that the driving roller and the idle roller of the discharge rollers are spaced part from each other, and returning the branch flap to an initial position thereof to allow a second sheet to be fed along the first feeding path, and allowing the driving roller and the idle roller of the discharge rollers to make contact with each other when a predetermined time has elapsed after a front end of the second sheet has passed through the sheet detecting sensor and rotating the driving roller and the idle roller of the discharge rollers in a forward direction such that the first and second sheets are simultaneously discharged out of the pair of the discharge rollers.

In addition, the sheet feeding apparatus having the buffer function can be simply installed on the sheet feeding path.

Further, the sheet feeding apparatus may have the stable buffer function without causing the jam of the sheets.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view illustrating the structure of a sheet processing apparatus of an image processing system according to the related art;

FIG. 2 is a perspective view of a sheet feeding apparatus having a buffer function according to the present invention;

FIG. 3 is an exploded perspective view of a sheet feeding apparatus having a buffer function according to the present invention;

FIG. 4 is a sectional view of a sheet feeding apparatus having a buffer function according to the present invention before a cam is driven;

FIG. 5 is a sectional view of a sheet feeding apparatus having a buffer function according to the present invention when a cam has been driven; and

FIGS. 6A to 6H are sectional views illustrating the operation of a sheet feeding apparatus having a buffer function according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the configuration and operation of the sheet feeding apparatus having the buffer function according to the present invention will be described in detail with reference to FIGS. 2 to 5.

The sheet feeding apparatus 100 includes a pair of discharge rollers 60 including a driving roller 20 and an idle roller 30, upper and lower guides 31 and 32 installed at upper and lower ends of the discharge rollers 60 to form a sheet discharge path, a sheet support guide 35 installed at a rear of the lower guide 32, and a pair of branch flaps 81 and 82 installed at a rear end of the paper support guide 35.

The branch flaps 81 and 82 form a first feeding path 40 to discharge sheets through the discharge rollers 60 or open/close a second feeding path 50 which branches rearward from an outlet of the first feeding path 40. As the discharge rollers 60 are reversely driven, the sheet is moved back and the second feeding path 50 serves as a passage for the sheet to guide the rear end of the sheet being moved back. The second feeding path 50 may be open or closed through the operation of the branch flaps 81 and 82.

A sheet detecting sensor 33 is installed at an upper portion of a rear end of the upper guide 31 in order to detect the rear end of the sheet moving along the sheet support guide 35. The sheet detecting sensor 33 can be installed on a bracket 34 fixed to the rear end of the upper guide 31.

Meanwhile, both ends of a rotating shaft 21 of the driving roller 20 are fixed to lower portions of cam holders 25 having a substantially rectangular shape.

A stepped section 26 making contact with a cam 70 is formed at an inner surface of an upper portion of each cam holder 25.

The cams 70 are fixed to both ends of the rotating shafts 71 in the cam holders 25 having the substantially rectangular shape.

If the cams 70 are not driven, as shown in FIG. 4, the stepped section 26 formed at an upper inner portion of the cam holder 25 may not make contact with the cam 70, so the idle roller 30 is engaged with the driving roller 20. However, as shown in FIG. 5, if the cams 70 are driven, the cams 70 make contact with the stepped section 26 formed at the upper inner portion of the cam holder 25, so the rotating shaft 21 of the driving roller 20 is lift up together with the cam holders 25. Thus, the idle roller 30 is spaced apart from the driving roller 20.

The rotating shaft 21 of the driving roller 20 is operated by a reversible motor (not shown), and the rotating shaft 71 of the cam 70 is operated by a separate motor (not shown), which is not interworking with the rotating shaft 21 of the driving roller 20.

Hereinafter, the method for buffering and feeding sheets using the sheet feeding apparatus 100 having the above structure will be described with reference to FIGS. 6A to 6H.

First, in a state that the cams 70 do not make contact with the cam holders 25, the branch flaps 81 and 82 close the second feeding path 50 and open the first feeding path 40 as shown in FIG. 6A, thereby allowing a first sheet 90 to be discharged through the first feeding path 40.

Then, as shown in FIG. 6B, if the sheet detecting sensor 33 detects the rear end of the first sheet 90 moving along the first feeding path 40, the branch flaps 81 and 82 are operated so that the second feeding path 50 is open as shown in FIG. 6C. At the same time, the discharge rollers 60 are reversely operated so that the rear end of the first sheet 90 is moved back by a predetermined distance along the second feeding path 50.

Even though the first sheet 90 has been moved back, the front end of the first sheet 90 must be positioned between the driving roller 20 and the idle roller 30.

Then, as shown in FIG. 6D, in a state that the rear end of the first sheet 90 has been moved back by the predetermined distance along the second feeding path 50, the cams 70 are driven to lift up the cam holders 25. Thus, the driving roller 20 is spaced apart from the idle roller 30, so that the feeding of the first sheet 90 is stopped.

After that, as shown in FIGS. 6E and 6F, the branch flaps 81 and 82 are operated such that a second sheet 91 can be fed toward the first feeding path 40. In this case, the driving roller 20 is spaced apart from the idle roller 30 until the front end of the second sheet 91 passes through the discharge rollers 60 along the surface of the first sheet 90 by passing through branch flaps 81 and 82. The entry of the second sheet 91 can be detected by the sheet detecting sensor 33 or an additional sheet detecting sensor (not shown).

Then, as shown in FIG. 6G, the cams 70 are driven such that the cams 70 can be spaced apart from the cam holders 25. Thus, the driving roller 20 makes contact with the idle roller 30 due to the tare thereof.

The cams 70 maybe spaced apart from the cam holders 25 in proper time by taking the distance between the sheet detecting sensor and the discharge rollers 60 and the sheet feeding speed into consideration after the entry of the second sheet 91 has been detected.

In a state that the driving roller 20 makes contact with the idle roller 30, if the driving roller 20 is normally driven (counterclockwise direction), the first and second sheets 90 and 91 can be simultaneously discharged.

Although it has been described that the two sheets are safely buffered and simultaneously discharged through the procedure shown in FIGS. 6A to 6H without causing the jam or the change of the discharge order, the present invention is not limited thereto. It will be understood to those skilled in the art that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 

What is claimed is:
 1. A sheet feeding apparatus having a buffer function, the sheet feeding apparatus comprising: a pair of discharge rollers including a driving roller and an idle roller; a first feeding path connected to the discharge rollers; a second feeding path located at a rear of the first feeding path while being branched from the first feeding path; a branch flap installed at a branch part of the first and second feeding paths; a sheet detecting sensor installed on the first feeding path between the branch flap and the discharge rollers; a cam holder for rotatably supporting both ends of a rotating shaft of the driving roller; and a cam for moving the cam holder up and down to allow the driving roller to selectively engage with the idle roller.
 2. The sheet feeding apparatus of claim 1, wherein the rotating shaft of the driving roller is connected to a reversible motor.
 3. The sheet feeding apparatus of claim 2, wherein the cam holder has a substantially rectangular ring shape having a stepped top surface, the cam is installed in an internal cavity of the cam holder, and the cam selectively makes contact with a stepped inner surface of the cam holder.
 4. A method for feeding sheets in a sheet feeding apparatus having a buffer function, the sheet feeding apparatus including a pair of discharge rollers including a driving roller and an idle roller, a first feeding path connected to the discharge rollers, a second feeding path located at a rear of the first feeding path while being branched from the first feeding path, a branch flap installed at a branch part of the first and second feeding paths, a sheet detecting sensor installed on the first feeding path between the branch flap and the discharge rollers, a cam holder for rotatably supporting both ends of a rotating shaft of the driving roller, and a cam for moving the cam holder up and down to allow the driving roller to selectively engage with the idle roller, the method comprising: discharging a first sheet outward through the pair of discharge rollers until a rear end of the first sheet is detected by the sheet detecting sensor as the first sheet is fed along the first feeding path; reversely driving the pair of discharge rollers as the sheet detecting sensor detects the rear end of the first sheet and moving back the first sheet by guiding the rear end of the first sheet to the second feeding path using the branch flap; driving the cam such that the driving roller and the idle roller of the discharge rollers are spaced part from each other, and returning the branch flap to an initial position thereof to allow a second sheet to be fed along the first feeding path; and allowing the driving roller and the idle roller of the discharge rollers to make contact with each other when a predetermined time has elapsed after a front end of the second sheet has passed through the sheet detecting sensor and rotating the driving roller and the idle roller of the discharge rollers in a forward direction such that the first and second sheets are simultaneously discharged out of the pair of the discharge rollers. 